Diabetes is one of a broad range of human diseases and disorders that are directly associated with endoplasmic reticulum (ER) malfunction. This malfunction is termed ER stress (ERS) and results from the accumulation of luminal unfolded/misfolded proteins. Cellular response to ERS is regulated by the Unfolded Protein Response (UPR) and will result in either ERS attenuation or apoptosis. ERS leading to cell death is often observed in type 2 diabetes when pancreatic p-cells are placed under high insulin production loads to maintain euglycemia. This proposal is focused on understanding the function and activity of the soluble 78 kDa Glucose-Regulated protein (GRP78) that serves as a molecular chaperone to facilitate protein folding in the ER lumen. GRP78 is a master regulator of UPR activity and thus plays a significant role in determining cellular response to ERS. To accomplish this objective we will utilize a novel family of small molecules called FlexHets that are now known to target GRP78 function. The focus in AIM 1 is to determine if FlexHet inhibition of GRP78 activity enhances insulin receptor signaling and response. AIM 2 is focused on determining the molecular basis for FlexHet binding to GRP78 as a means to understand GRP78 function and regulation by small molecule therapeutics. AIM 3 uses in vivo mouse models to determine if GRP78 inhibition modulates ERS response and signaling in obese vs. non-obese diabetic mice. Thus, our approach is to combine a range of in vitro and in vivo methods to develop a holistic model of GRP78 function by utilizing FlexHets as a targeted molecular tool to inhibit GRP78 function and activity. GRP78 has been previously shown to play a key role in insulin signaling using heterozygous knockout mice so the current studies are aimed at understanding the molecular basis for this observation and vetting GRP78 as a viable candidate for therapeutic intervention in the treatment of type 2 diabetes.